I lost 20kg about 6 years ago now and have pretty much maintained it without dieting or maintaining an exercise regime. My biggest thing was constanly snacking on crap (through boredom) and soft drink. I have a huge sweet tooth and find that denying it makes me want it more so I still eat alot of sweet food, I just make sure that everything else I eat is good. I also walk alot, it is my thing. I hate running, I hate gyms, I don't like organised things. I like just walking.

The problem is what works for me wont work for everyone. Do what you find comfortable and try and see it more as a lifestyle change then a diet.